December 9, 2014

Monkeying Around With Math – Dopamine Plays A Role In Cognitive Reasoning

Dopamine is probably best known as the neurotransmitter that brings us happiness, contentment or pleasure, but a new study from researchers at the University of Tübingen’s Institute for Neurobiology in Germany has shown that dopamine also plays a role in cognitive tasks.

Published in the journal Neuron, the new study specifically found that dopamine plays a role in the brain’s processing of mathematics.

Previous research has shown that dopamine plays a role in motor skills as individuals suffering from Parkinson’s disease have markedly lower levels of the neurotransmitter in their brains. Researchers have also known that a dopamine imbalance can disrupt cognitive abilities – particularly in the prefrontal cortex, which is used in logical processing.

In the new study, researchers taught rhesus monkeys to answer simple “greater than” and “less than” math questions. Utilizing recent research as a basis, the scientists knew that particular neurons in the prefrontal cortex are involved in answering these kinds of questions. Studies show that one side of these “rule cells” in the prefrontal cortex is triggered when the “greater than” rule is used, and the other side is triggered when the “less than” rule applies.

As these cells are being turned on, relatively small quantities of various substances were being released nearby. These chemicals can have the same impact as dopamine - or the reverse - and could interact with dopamine-sensitive neurons. The team saw that activation of the dopamine system permitted the “rule cells” to execute their function better and to better differentiate between the “greater than” and “less than” rules.

Nerve cells in the prefrontal cortex (marked) can process “greater than” and “less than” rules better under the influence of dopamine. Credit: LS Tierphysiologie/Tübingen University

The study team said their work provides new details on how dopamine affects abstract thought processes – such as those required for the use of simple mathematical rules.

“With these findings, we are just starting to understand how nerve cells in the prefrontal cortex produce complex, goal-directed behavior,” said study author Torben Ott, a neurobiologist at University of Tübingen.

Andreas Nieder, also from Tübingen, noted that his team’s results could also have medical significance.

“These new insights help us to better interpret the effects of certain medicines which may be used for instance in cases of severe psychological disturbance,” Nieder said, “because such medications influence the dopamine balance in the prefrontal cortex in ways we do not understand well to date.”

Dopamine is often associated with drug and alcohol use, and a study last year showed that simply tasting alcohol can release a flood of dopamine completely independent from any effect the alcohol might have. The study team found this effect was much stronger in people with a family history of alcoholism.

“Sensory cues that are closely associated with drug intoxication (ranging from tastes and smells to the sight of a tavern) have long been known to spark cravings and induce treatment relapse in recovering alcoholics. Many neuroscientists believe dopamine plays a critical role in such cravings,” the study team said in a statement.

“We believe this is the first experiment in humans to show that the taste of an alcoholic drink alone, without any intoxicating effect from the alcohol, can elicit this dopamine activity in the brain’s reward centers,” said David A. Kareken, a professor of neurology at the Indiana University.